
package jweslley.ContestVolumes.VolumeCII;

import static java.lang.Math.PI;
import static java.lang.Math.sin;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.NumberFormat;

import jweslley.Problem;
import jweslley.Problem.Status;

/**
 * http://icpcres.ecs.baylor.edu/onlinejudge/external/102/10286.html
 *
 * @author  Jonhnny Weslley
 * @version 1.00, 23/10/2008
 */
@Problem(Status.Accepted)
public class TroubleWithAPentagon {

	public static void main(String[] args) throws IOException {
		DecimalFormatSymbols symbols = DecimalFormatSymbols.getInstance();
		symbols.setDecimalSeparator('.');
		NumberFormat format = new DecimalFormat("##0.0000000000", symbols);
		StringBuilder out = new StringBuilder();

		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String line; double input;
		while ((line = in.readLine()) != null) {
			input = Double.valueOf(line);
			out.append(format.format(sin(108*PI/180.0)/sin(63*PI/180.0)*input)).append('\n');
		}
		System.out.print(out);
	}

}
